First Lebanon War

The First Lebanon War occurred from 6 June 1982 to June 1985 when Israel invaded Lebanon with the goal of expelling the Palestine Liberation Organization from its new base of Beirut. Israel's invasion occurred amid the highly-destructive Lebanese Civil War, and Israel was forced to fight against not just the PLO, but also against the Syrian Arab Army and several Lebanese militias while being supported by the Maronite Christian Lebanese Front and the South Lebanon Army. In August 1982, the PLO was forced to relocate to Tunisia, while the Israelis installed the Maronite Bachir Gemayel as their puppet President of Lebanon. However, Gemayel was assassinated by the SSNP in September 1982, and Israel was forced to withdraw from Lebanon in June 1985 due to its failure to create a popularly-supported allied government in the country; it continued to occupy South Lebanon for fifteen years, leading to the South Lebanon conflict.

Background
In 1968, the Palestine Liberation Organization relocated to South Lebanon on Israel's northern border, launching guerrilla raids, rocket strikes, and terrorist attacks on Israel from several new Palestinian refugee camps. Following the 1978 Coastal Road massacre, the Israeli IDF launched Operation Litani, invading South Lebanon and driving the PLO from their bases in the south, forcing them to relocate to the Lebanese capital of Beirut. The Israelis were upset that the PLO was able to survive the initial invasion, and the presence of United Nations peacekeepers in South Lebanon was ineffective in preventing PLO attacks on Israel, as both the PLO and the pro-Israel Christian South Lebanon Army sporadically attacked the UN forces. From July 1981 to June 1982, the PLO launched 270 terrorist attacks on northern Israel. On 3 June 1982, the Israeli ambassador to the United Kingdom, Shlomo Argov, was seriously wounded in an assassination attempt by Palestinian gunmen affiliated with the pro-Iraq Abu Nidal Organization, and Israeli prime minister Menachem Begin used this incident to justify a retaliatory invasion of Lebanon to destroy the PLO, even though the PLO were rivals with the ANO and were not responsible for that specific attack.

Initial invasion
On 6 June 1982, 60,000 IDF troops and over 800 tanks invaded South Lebanon on three fronts, planning to push back PLO forces 25 miles to the north. One Israeli force planned to destroy three PLO camps near the coastal city Tyre and then advance up the coast towards Sidon and Damour, while the central Israeli force advanced to take Beaufort Castle and then the Nabatieh road junction, and the eastern Israeli force would advance into the Bekaa Valley to prevent Syrian reinforcements from supporting the PLO.

The advance along the coast was preceded by heavy artillery bombardment and airstrikes, but the Israeli armor was caught in a traffic jam due to the narrowness of the coastal road, and the PLO ambushed the armor with anti-tank weaponry and knocked out several tanks. The IDF managed to take Beaufort Castle that same evening after heavy fighting, losing 6 men and killing 24 PLO militants; the Nabatieh road junction was secured before the day was done. At the same time, Israeli forces advanced into the Bekaa Valley, and the Syrians put up little resistance. Apart from the delayed coastal advance, the Israeli operation was on track to succeed. The Israeli Air Force used cluster bombs to bombard PLO positions along the coastal road, and Israeli missile boats fired 3,500 shells during ten days of fighting. As Israeli armor advanced on Sidon, IDF troops attacked the PLO bases at the Rashidiya, Burj ash-Shamali, and al-Bass refugee camps, urging civilians to leave before heavily bombarding the bases and assaulting the camps in close-quarters urban combat. Soon, 2,400 IDF troops and 400 tanks were landed on the Lebanese coast, advancing on Sidon. The PLO put up heavy resistance in Sidon itself and in the Ain al-Hilweh refugee camp, and the Israelis decided to bypass and besiege the city. Meanwhile, in the Battle of Jezzine, the central Israeli force defeated the Syrians in a fierce armored battle. In Operation Mole Cricket on 9 June 1982, the IAF shot down 29 Syrian Air Force planes and destroyed 17 Syrian SAM batteries, and the IAF also destroyed a Syrian armored brigade moving south from Baalbek. Israeli soldiers advanced up the Beirut-Damascus Highway, pushing through the Syrian defenses; on 11 June, Syria agreed to a ceasefire with the Israelis. However, the Syrians violated the ceasefire with further attacks on the Israelis, so the Israelis resumed their advance on Beirut. On 13 June, the Israelis bypassed the PLO defenses at Khalde and advanced on Baabda, which overlooked Beirut's airport. The Israelis broke through the Syrian positions and captured Baabda, and they also took Shuweifat, cutting the Beirut-Damascus Highway and besieging the PLO and Syrian forces in the city. From 16 to 22 June, both the Israelis and Syrians reinforced their troops along the highway. On 22 June, the IDF launched an operation to take the highway, destroying 130 Syrian vehicles and positions in a single air attack. The Israelis trapped a large Syrian force, forcing the Syrians to flee as their positions collapsed. The Israelis later encountered fierce resistance from Iranian volunteers for the PLO at Aley. On 24 June, the Israelis began to shell the outskirts of Chtaura at the northern mouth of the Bekaa Valley, forcing the Syrians to withdraw a day later and removing the last major obstacle between the Israelis and the Syrian capital of Damascus.

Siege of Beirut
On 14 June 1982, the Israelis besieged Beirut rather than engage in costly street fighting, bombarding Beirut from the sea, land, and air. In August 1982, the PLO agreed to evacuate its 14,000 fighters from the city, supervised by UN peacekeepers; 6,500 Fatah fighters relocated to Jordan, Syria, Iraq, Sudan, Yemen, Greece, and Tunisia, and Yasser Arafat relocated the PLO's main base to Tunis in Tunisia. Israel thus achieved its goal of routing the PLO from Lebanon.

Israeli withdrawal
The April 1983 United States embassy bombing and other attacks on UN peacekeeping forces by Iranian-backed Islamist guerrillas forced the international peacekeeping forces to withdraw from Lebanon. The Islamists then began launching guerrilla attacks against the Israeli occupation forces, with suicide bombings being popular tactics; the Tyre headquarters bombings killed 103 IDF personnel and 56 Lebanese civilians. The IDF then withdrew to the south of the Awali River, but the Islamic militias spread their operations to South Lebanon, where they attacked both the IDF and their Maronite allies. The disorganized Islamic militants in South Lebanon united as "Hezbollah", which became a dangerous threat to Israel. In February 1985, Israeli forces evacuated Sidon, and the Israelis continued to suffer heavy losses to Islamist attacks. Israel withdrew from the Bekaa Valley on 24 April 1985 and from Tyre on 29 April, and, in June 1985, the IDF and the South Lebanon Army withdrew to a security zone in southern Lebanon, ending the First Lebanon War and starting the South Lebanon conflict.